The invention relates to a distributor plate for fluidized bed equipment with openings and deflector strips arranged directly above them.
Bulk materials are treated (dried, cooled, tempered, . . . ) in fluidized bed equipment. The material to be treated enters the equipment, is fluidized and then conveyed in a statistical distribution to the overflow. The underflow is used to empty out and discharge the coarse material. Fluidization is effected by the gas conveyed into the air boxes by a fan, and which flows evenly through the distributor plate into the product layer. The gas leaves the equipment through the dedusting unit, sucked in by a fan.
In order to ensure even distribution of the gas volume flow into the fluidized bed equipment, distribution plates of different designs are used. The distribution plates combine one or more functions to enable stable equipment operation.
These include:                Even distribution of the gas flow over the surface, also with different counter-pressures in places in the fluidized bed as a result of bubbles forming, secondary air currents, etc.        Separation of air chamber (air box) and product layer, especially to prevent the product from trickling through into the air chamber.        Avoidance of dead surfaces with no gas flowing through because the product would collect here and could suffer from thermal damage and inadequate product exchange in the fluidized bed.        Conveying of particles that cannot be fluidized adequately due to their size and descend onto the distributor plate.        
Even gas distribution is achieved by the distributor plate having an adequate pressure drop in relation to the pressure fluctuations occurring in the product layer. Ideally, this is achieved by accelerating the flow with as little loss as possible, i.e. by converting the pressure energy into kinetic energy as completely as possible so that there is a maximum transfer of impulse to the particles (CH 629394).
In practice, pressure losses of 50-300 daPa are used frequently because they form a good compromise between operational reliability and energy requirement.
This means that the distributor plates used have a free cross-section with air flowing through typically measuring 0.5-15% of the total surface area.
This is achieved by means of sieve, sintered, perforated, or punched plates whose free cross-section is distributed finely over the entire surface, or by means of nozzle plates, where the free cross-section is concentrated in a few nozzles.
During operation, the product should not trickle through if the pressure loss is dimensioned correctly and the openings are not too big. During shutdown, however, this must be guaranteed by the geometry, for example very small holes (depending on the particle diameter, but frequently<approx. 0.2 mm in perforated, sieve and punched plates), which tend, however, to cause clogging in circulating gas operation, or by covering (larger than the bulk material cone) the openings with discs, strips, and so on (cf. EP 0103708, CH 629394). Self-closing nozzles are also known, from column technology for example (gas-liquid fluidized bed).
During operations, however, the product settles on these coverings because the surfaces are on the slipstream side. This is prevented by mounting displacement bodies on these surfaces (cf. EP 0215327, EP 0103708). As a result, greater effort is required and, if the strips are mounted at right angles to the main conveying direction of the product, there will be additional resistance when conveying coarse material.
There are solutions for conveying inadequately fluidized coarse material that have been implemented technically. Conveying can be assisted mechanically on the one hand by causing the entire fluidized bed equipment to vibrate or only the air boxes or distributor plates. In order to avoid this considerable design effort and other disadvantages, a pneumatic conveying effect is achieved with an appropriate distributor plate design.                In stamped metal plates, asymmetrical tools create a hole that is open on one side which allows the gas to flow forwards and upwards on a slant, thus effecting an impulse transfer to the particles parallel to the distributor plate (brand names include Conidur, Coniperf).        In nozzle plates with rotationally symmetrical gaps, the gas generally flows parallel to the base plate anyway, but in all directions. By closing off at least half of the gap by means of a suitable shim, it is possible to set any desired outflow direction, and thus also conveying direction.        In nozzle plates with covered cross-direction gaps, the conveying direction is dictated by the arrangement of the gaps. Conveying is obstructed, however, by the cover strips arranged in cross direction.        
The state-of-the-art distributor plates have disadvantages, however, that are avoided by using the embodiment according to the invention:                Due to manufacturing reasons, punched bases only have small sheet thicknesses and are thus sensitive to wear and extreme temperatures, which limits their possible applications.        The impulse of the gas flow exiting at high speed is dispelled by the fluidized bed after only a few centimetres; a large number of closely distributed nozzles are needed in order to continue conveying, and this means additional effort and more obstacles.        nozzle plates with gaps in cross direction tend to form deposits on the cover strips, and it is not possible to mount displacement bodies without further obstructing conveying operations.        